Scientists have been working tirelessly to develop a vaccine for HIV since the deadly virus stormed into the world’s consciousness in the 1980s. Many researchers now believe that the scientific community has come closer than ever to just that — developing an HIV vaccine that could potentially inoculate billions, and guard them against ever acquiring the virus.

The study was conducted by the Ministry of Health in Thailand in coordination with the U.S. Army, and while the potential vaccine was only moderately successful against two strains of a highly mutable virus, it was the first documented successful case on record. Some 16,000 HIV-negative Thais volunteered to take part in the trial between 2003 and 2006. Half were given test vaccines and the other half placebos, without any knowledge of which they received. Subjects were then tested every six months. From those who took the placebo, 74 became infected with HIV, compared with only 51 who took the vaccine, a 31-per-cent efficiency rate.

Researchers caution the test results are hardly definitive and aren’t even fully understood yet. Many prominent scientists are questioning them altogether. Moreover, a ready-to-license vaccine is likely years away, but the progress is promising and scientists hope it catapults future studies forward.

What does this mean for you, right now? Not much. If you’re having sex, use protection.